The invention relates to fittings for connecting heavy mooring ropes to buoys or ships, particularly fittings large enough to accept the large diameter ropes used to secure tankers and other large ships to single point mooring buoys.
Mooring of ships, especially enormous ships such as super-tankers, by means of synthetic ropes and associated hardware presents problems which are a whole order of magnitude different from those encountered in the conventional prior practice. The ropes used may be from 2" (48 mm) to 10" (240 mm) in diameter and the hardware (usually of expensive material such as stainless steel) instead of weighing a few pounds may be of the order of thousands of pounds and correspondingly vastly more costly. Since the massive and expensive hardware, shackles, swivels, thimbles, etc., in normal use have a longer useful life than the ropes it is desirable to re-use rather than to discard them when the rope becomes unsafe through wear and this poses the problem of attaching fresh rope to hardware, possibly at some remote port in the world, without the availability of expert assistance and equipment. Ropes of the diameters in question are not readily eye-spliced and the eyes fitted properly to conventional thimbles without trained personnel and special equipment.
It has been proposed to encapsulate in suitable plastic at the factory the eye of an eye-spliced rope together with a thimble in which it has been inserted so that the thimble not only supports the inner surface of the eye but provides surrounding metal to protect the outer surface of the rope against damage or abrasion. The result is a factory-prepared and shipped rope or hawser with a very heavy and expensive thimble at each end, the thimble and the eye portion of rope therein being together encapsulated in plastic to form a long-wearing, but heavy, fitting for connection by a shackle to other hardware. When the rope becomes too worn for use the heavy stainless steel plastic encapsulated eye containing thimble can be cut off and shipped back to the cordage manufacturer for cleaning out (a difficult task) for ultimate re-use on the end of a fresh rope. This burdensome procedure can be economically justified only because of the value of the thus reclaimed hardware.
Furthermore, the conventional thimble shape provides only a very sloppy joint between shackle bolt and thimble surface and the bolt will undergo rapid wear by rubbing on this surface in cases where a vessel, moored with a rope equipped with such a thimble, is subjected to enormously large forces from wind, wave, and current.